The present invention relates to a copier with a both- or double-face copying function, a variable-magnification copying function, and a bookbinding function for binding a stack of copy papers at their center or edge. More particularly, the present invention relates to a copier with a bookbinding ability which allows copies to be selectively bound at their center and edge and, in the former case, stacks the papers folding them double together and, in the latter case, stacks them in a straight position.
In a copier of the type described, where it is desired to produce a plurality of copies for each of a plurality of documents, use has been made of a sorter to sort copies in the order of pages and a stitcher to bind the copies along their aligned edges.
The problem with such a prior art system is that binding or stitching relatively large sheets such as those of format A3 or B4 along their aligned edges results in a booklet which occupies a substantial space or area when opened and, so, is awkward to handle. In addition, while relatively large sheets are sometimes double-folded after being bound along the edge in order to save the space for storage, folding bound sheets double together not only degrades their appearance in storage but also makes information carried in the folded portions difficult to see due to the folds.
Although the problem mentioned above may be overcome by binding papers at their center, binding sheets at the center needs to be preceded by creasing them at the center. Specifically, one approach to bind papers at the center is creasing each paper discharged from a copier by folding it double, stacking the so creased papers over predetermined number of pages, and stitching them along the creases to provide a booklet. However, since the crease varies in position from one size of sheets to another and even from one condition of sheet and document transfer to another, it is difficult to crease and bind many different sizes of sheets together at an exactly desired position. It is also difficult to stack creased sheets one upon another in an ordary appearance.
Furthermore, where copy papers are bound at their center and, then, stacked as they are, the papers pile up in an open position so that one has to pick them out and, thereafter, fold them double by awkward manipulation. As for those papers which were bound at their aligned edges, it is desirable that they be stacked without being bolded double.
In addition, should the bookbinding function be exclusively designed for binding papers at the center, the need for binding papers at an edge which often arises could not be satisfied without using an exclusive edge binding device at the cost of performance.